Correction: The original version of this post misattributed a quote to Defense Secretary Ash Carter. Jeff McCausland, a retired Army colonel and former dean at the Army War College, said Trump didn’t “know a damn thing about military strategy.” TPM regrets the error.

Responding to a retired Army colonel who claimed Donald Trump didn’t “know a damn thing about military strategy,” the Republican nominee said “I’ll teach him a couple of things.”

“The Army War College–” Trump began in a Wednesday interview with ABC’s George Stephanopoulos, responding to the dig from Jeff McCausland, a retired Army colonel and former dean at the Army War College. “Let me tell you, the element of surprise, I’ve been hearing about Mosul now for three months.”

“Why do they have to talk about it? Don’t talk about it. Element of surprise,” Trump continued, telling Stephanopoulos that Gens. George Patton and Douglas MacArthur, famous for their leadership during World War II, would not have announced an invasion of the Iraqi city of Mosul in advance.

“They wanted to get the ISIS leaders who they thought were in Mosul. Those people have all left. As soon as they heard they were going to be attacked, they left,” Trump said.

When Stephanopoulos said that Secretary of Defense Ash Carter reported Tuesday that 35 Islamic State leaders had been killed in the run-up to the Mosul offensive, Trump scoffed.

“Don’t talk about it,” the Republican presidential nominee added. “Element of surprise. So you can tell your military expert that I’ll sit down and I’ll teach him a couple of things.”

But Trump’s assumption that ISIL leaders wouldn’t know about the Mosul offensive if American military officials hadn’t announced it has been called into question by experts.

“An ISIS that didn’t know there’d be an attempt to retake Mosul would be an ISIS that was too stupid to have taken Mosul in the first place,” Professor Stephen Biddle, a professor of political science and international relations at George Washington University, told Vox. “If ISIS wasn’t already preparing, they’d be guilty of military negligence, and we would be delighted that they’re so incompetent.”